SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF CHITOSAN/CLAY NANOCOMPOSITES
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Clay-based bionanocomposites have gained great attention due to their nanosized functional properties and safe natural structures. Combination at the nanometric scale of the increased surface areas and reactive surfaces of clays with the functional behavior of biopolymers has been pointed out as an attractive way to develop organic-inorganic nanohybrid materials with properties that are inherent to both types of components. In this study a natural-based nanocomposite film consisting of chitosan and organic clay was synthesized. Montmorillonite modified with octadecylamine (ODA-MMT) was used as an organically modified layered silicate. The nanocomposite was prepared by mixing a acetic acid suspension of ODA-MMT with a solution containing chitosan as the macroscopic polymer matrix. The effect of ODA-MMT content (0.5-3%) on the structure and antimicrobial activity of the nanocomposite have been investigated. The interactions between the chitosan matrix and ODA-MMT at different conditions were evaluated using SEM, TEM, XRD and DSC analysis. The results indicated that the formation of exfoliated nanostructure and the thermal stability of nanocomposites was improved within increased loading of nano-dispersed clay in matrix. Antimicrobial activity of chitosan/ODA-MMT nanocomposites was evaluated using disc diffusion method against Gram-positive bacteria Staphylococcus aureus ATCC 25923 and Streptococcus mutans ATCC 25175 and Gram-negative bacteria Escherichia colt ATCC 25922 and Salmonella spp. (Laboratory stock). The antimicrobial activity studies of the nanocomposites showed that the nanocomposites could more strongly inhibit the growth of the tested Gram-positive bacteria than Gram negative bacteria. The inhibitory effect of nanocomposites on microorganisms increased with the increasing content of ODA-MMT. The results showed that the strong antimicrobial activity of the nanocomposites may be related to the interaction and the fine dispersion between chitosan and clay.